Java反射获取对象VO的属性值（通过Getter方法）

有时候，需要动态获取对象的属性值。

比如，给你一个List，要你遍历这个List的对象的属性，而这个List里的对象并不固定。比如，这次User，下次可能是Company。

e.g. 这次我需要做一个Excel导出的工具类，导出的批量数据是以List类型传入的，List里的对象自然每次都不同，这取决于需要导出什么信息。

为了使用方便，将对象的属性名与属性值存于Map当中，使用时就可以直接遍历Map了。

此次的思路是通过反射和Getter方法取得值，然后记录在一个Map当中。

Kick start...

将对象的属性名与属性值存于Map当中，以key，value的形式存在，而value并不希望以单一类型（如String）存在（因为涉及多种类型），所以用一个FieldEntity的自定义类（此类包含属性名，属性值，属性值类型 等属性）

 package com.nicchagil.util.fields;

 import java.util.ArrayList;
 import java.util.List;

 public class FieldEntity {

     // field name
     private String fieldname;

     // field value
     private Object value;

     // field value's class type
     private Class clazz;

     private List<String> errorMsg = new ArrayList<String> ();

     public String getFieldname() {
         return fieldname;
     }

     public void setFieldname(String fieldname) {
         this.fieldname = fieldname;
     }

     public Object getValue() {
         return value;
     }

     public void setValue(Object value) {
         this.value = value;
     }

     public Class getClazz() {
         return clazz;
     }

     public void setClazz(Class clazz) {
         this.clazz = clazz;
     }

     public List<String> getErrorMsg() {
         return errorMsg;
     }

     public void setErrorMsg(List<String> errorMsg) {
         this.errorMsg = errorMsg;
     }

     public FieldEntity() {
         super();
     }

     public FieldEntity(String fieldname, Object value, Class clazz) {
         super();
         this.fieldname = fieldname;
         this.value = value;
         this.clazz = clazz;
     }

     private FieldEntity(String fieldname, List<String> errorMsg) {
         super();
         this.fieldname = fieldname;
         this.errorMsg = errorMsg;
     }

     @Override
     public String toString() {
         return "FieldEntity [fieldname=" + fieldname + ", value=" + value
                 + ", clazz=" + clazz + ", errorMsg=" + errorMsg + "]";
     }

 }

 FieldEntity

主类，通过这个类的静态方法获取结果Map

 package com.nicchagil.util.fields;

 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.HashMap;
 import java.util.Map;

 public class FieldsCollector {

     public static Map<String, FieldEntity> getFileds(Object object)
             throws SecurityException, IllegalArgumentException, NoSuchMethodException,
             IllegalAccessException, InvocationTargetException {
         Class clazz = object.getClass();
         Field[] fields = clazz.getDeclaredFields();
         Map<String, FieldEntity> map = new HashMap<String, FieldEntity> ();

         for (int i = 0; i < fields.length; i++) {

             Object resultObject = invokeMethod(object, fields[i].getName(), null);
             map.put(fields[i].getName(), new FieldEntity(fields[i].getName(), resultObject, fields[i].getType()));
         }

         return map;
     }

     public static Object invokeMethod(Object owner, String fieldname,
             Object[] args) throws SecurityException, NoSuchMethodException,
             IllegalArgumentException, IllegalAccessException, InvocationTargetException {
         Class ownerClass = owner.getClass();

         Method method = null;
         method = ownerClass.getMethod(GetterUtil.toGetter(fieldname));

         Object object = null;
         object = method.invoke(owner);

         return object;
     }

 }

 FieldsCollector

为了代码清楚些，将一些工具方法独立一下，如field name到getter name的转换方法

 package com.nicchagil.util.fields;

 public class GetterUtil {

     /**
      * Get getter method name by field name
      * @param fieldname
      * @return
      */
     public static String toGetter(String fieldname) {

         if (fieldname == null || fieldname.length() == 0) {
             return null;
         }

         /* If the second char is upper, make 'get' + field name as getter name. For example, eBlog -> geteBlog */
         if (fieldname.length() > 2) {
             String second = fieldname.substring(1, 2);
             if (second.equals(second.toUpperCase())) {
                 return new StringBuffer("get").append(fieldname).toString();
             }
         }

         /* Common situation */
         fieldname = new StringBuffer("get").append(fieldname.substring(0, 1).toUpperCase())
                 .append(fieldname.substring(1)).toString();

         return  fieldname;
     }

 }

 GetterUtil

大功告成！！！

现在，写个VO作为模拟数据

 import java.util.Date;

 public class User {

     private String username;
     private String password;
     private String eBlog;
     private Date registrationDate;

     public String getUsername() {
         return username;
     }

     public void setUsername(String username) {
         this.username = username;
     }

     public String getPassword() {
         return password;
     }

     public void setPassword(String password) {
         this.password = password;
     }

     public String geteBlog() {
         return eBlog;
     }

     public void seteBlog(String eBlog) {
         this.eBlog = eBlog;
     }

     public Date getRegistrationDate() {
         return registrationDate;
     }

     public void setRegistrationDate(Date registrationDate) {
         this.registrationDate = registrationDate;
     }

 }

 User

最后，测试类，此类将直接调用FieldsCollector~~

 import java.util.Date;
 import java.util.Map;

 import com.nicchagil.util.fields.FieldEntity;
 import com.nicchagil.util.fields.FieldsCollector;

 public class Call {

     public static void main(String[] args) throws Exception {

         User user = new User();
         user.setUsername("user109");
         user.setPassword("pwd109");
         user.seteBlog("http://www.cnblogs.com/nick-huang/");
         user.setRegistrationDate(new Date());

         Map<String, FieldEntity> map = FieldsCollector.getFileds(user);
         System.out.println(map);

     }

 }

 Call

原文作者：Nick Huang 博客：http://www.cnblogs.com/nick-huang/

参考http://www.cnblogs.com/nick-huang/p/3831849.html